Joop Schaye (Leiden) (Yope Shea) Before we even got started, we - - PowerPoint PPT Presentation

Joop Schaye (Leiden) (Yope Shea)

Before we even got started, we were shown that the process of shocking… … can lead to quenching … … or (temporary?) quiescence …

… but that it can also trigger the formation of stars … … and alien life forms ?

Mechanisms:

Van den Bosch

Are satellite-specific quenching mechanisms required?

• Wilson, vd Bosch:

Quenched fraction depends both on galaxy and environment, separable at z=0

• Wilson:

– Stellar mass acts as dimmer – Environment acts as switch

• Moster, Behroozi, Rudnick:

Satellites are like

Are satellite-specific quenching mechanisms required?

• Somerville: SAMs use them, but quench

satellites too effectively

• Van den Bosch: Hearin/Watson showed that

abundance + age matching reproduces

• bservations.

– Subhalo formation time is all that matters – No need for satellite specific processes

Watson+ ‘14

Do massive galaxies grow more than we thought?

• Bernardi: Sky subtraction,

aperture size, choice of Sersic fit, M/L at fixed IMF all important. Decline of mass function less steep than before.

• Crain: Models may not need

changing, need to do comparison properly.

• Less quenching? Outer parts

probably accreted  formed in lower mass galaxies!

Do massive galaxies grow more than we thought?

• Dutton: Dense galaxies have

bottom-heavy IMF  more massive than we thought

• Note:

– IMF would then vary with radius  most of the extra mass may have more ordinary IMF – Models and observations care mostly about massive stars. Low- mass stars only affect gas consumption and gravity  no big changes needed to accommodate bottom-heavy IMF

Do massive galaxies grow more than we thought?

• Kaviraj: UV observations indicate that SF in ETGs

adds 30% of stellar mass after z~1.

• Davis:

– > 22% of Es have molecular gas, which is forming stars at relatively low efficiency (Martig: Morphological quenching) – Kinematics suggest gas has external origin (accreted or cooled as opposed to stellar mass loss) – No cold gas in slow rotators (i.e. most massive Es)

What do quenched galaxies look like?

• Bell, van der Wel, Somerville, Bernardi:

– ns > 2.5 – Large B/D (Jahnke: bulge not an active player) – M* > 3e9 M if central – Oblate/triaxial axis ratio – High surface density – High velocity dispersion – Compact

How/when are galaxies quenched?

• Somerville/Schawinski: Observations indicate

quenching + morphological transformation go together.

Halo quenching

• Birnboim/van de Voort: Change of accretion

mode at ~1012 M

• Van de Voort: Transition to hot halo does not

quench by itself, need AGN

• Why then do quenched galaxies live in haloes

with M > 1012 M ?

– SAMs (Fanidakis/Somerville): Affects accretion mode, BH fed by hot halo  radio mode. Works well for galaxy and BH properties. Not for ICM? – Questions: Why would BH mode care about accretion

• nto galaxy? Could it be that the same feedback
• perates differently in a hot halo?

Anything Goes Now feedback?

• Enormous amount of energy to play

with: 0.1 𝑁𝐶𝐼𝑑2 ≫ 𝑁∗,𝑐𝑣𝑚𝑕𝑓𝜏2

• Black hole radius of influence

completely unresolved  anything goes!

Anything Goes Now feedback?

However, we do have some understanding (King, Costa):

• Outflow first momentum-driven, but

becomes energy-driven at ~ 102 pc

• Expect ~ 5% of radiated energy to be

coupled  Thermal bomb on a scale ~ resolution

• f simulations

Anything Goes Now feedback?

If BH growth is self-regulating, as in most models, then freedom is severely limited (Croft, Teyssier):

• BH mass is the only thing that depends on fraction
• f accretion energy that is in the bombs
• Result insensitive to details like accretion and

seeding, provided the BH grows in absence of feedback Jahnke: BH scaling relations result of merging, not self-regulation However:

– Sensible for quenched galaxies, but Soltan argument implies gas accretion drives growth for active galaxies? – Very important to extend BH scaling relation to star- forming galaxies

Varying the efficiency of AGN feedback

Booth & JS (2009, 2010) Also Teyssier talk

Anything Goes Now feedback?

• Stellar mass dependent on assumed

efficiency of feedback from star formation

• Efficiency (thermal losses) cannot be

predicted until structure of ISM is resolved  Stellar feedback is no less (more?) “anything goes” than AGN feedback

Evidence for quasar-mode feedback:

• Zakamska: High-L radio-quiet QSOs

surrounded by spectecular OIII nebulae.

– Spectra suggest outflow of ~800 km/s over ~10 kpc. – Energy in outflow accounts for ~ 2% of LAGN

Can AGN quench disks?

• Difficult because outflow takes path of

least resistance (Cielo, Costa)

• Hot bubble may induce rather than halt

SF (King)

• Fortunately, we heard that observations

indicate that they do not have to:

– Only Es need to be quenched fast (Schawinsky, Somerville) – Disk SSFRs independent of M*  tilt of MS due to change in B/T (Abramson+ ‘14)

Radio mode (= maintenance mode?)

• La Franca: No radio loud/radio quiet bimodality
• Strong evidence that ICM knows about radio mode

(Pfrommer, Canning, Gallaghar)

– Is the cool gas uplifted or does it condense out? Probably the latter (Canning, Gallaghar) – Does cool gas trigger the AGN or does the jet trigger cooling? Second option would not give self-regulation…

• Cosmic ray heating (Pfrommer)

Can radio mode be the quenching mechanism?

• Quenching must happen in low-mass groups,

not clusters

• Can low fgas within R500 be caused by buoyant

bubbles?

• Radio mode operates when BH growth is slow

 Difficult to explain BH scaling relations

Maintenance: Balancing cooling w/o AGN:

• Conduction: no (O’Shea, Hopkins)
• Stellar mass loss: no, may even make it

harder (Hopkins, Bregman)

• Gravitational heating: no (Hopkins)
• SNIa (bulge/low-mass Es): yes (Bogdan,

Groves)

CGM

• Cool/warm gas (absorption):

– Not much difference between red and blue galaxies, except for OVI (Werk) – Lots of gas and metals around galaxies (Werk, Hennawi) – Complexity not captured by simulations (Hennawi)

• Hot gas in emission (Anderson):

– No break in X-ray scaling relations from clusters to galaxies – Hot gas around isolated Es does not account for missing baryons

Radiation

• Sources: AGN (Lusso), X-ray binaries, WDs (Gilfanov),

(Post-)AGB (Marigo)

• HeII4686 rules out accreting WDs as progenitors of

SNIa (Woods)

• LINERS are mostly not AGN  don’t just throw them
• ut of your sample (Singh)
• Gnedin: Usually unimportant and don’t need radiative

transfer where it matters

Damping/self-regulation

• Photo-ionisation by XRBs suppresses CGM cooling rate,

changes transition from cold to hot accretion (Cantalupo, Kannan)

– Note: scales as SFR  regulation rather than quenching

• Non-equilibrium can slow down (or speed up) cooling.

Cannot just assume ionisation/chemical equilibrium (Richings)

• Martig: Morphological transformation accompanied by

Morphological Quenching (Damping?). Bulge stabelizes disk due to lower disk mass and larger shear/Coriolis.

• Meidt: Streaming motions reduce SF efficiency

Look at stars and CGM simultaneously

(Cosmo-)OWLS: Le Brun+ ’14; McCarthy+ ‘10

Amount of feedback energy less important than the manner in which it is injected!

Thermal bomb AGN FB works

(Cosmo-)OWLS: Le Brun+ ’14; McCarthy+ ‘10 Stellar metallicities too low, rest works well

How does thermal bomb AGN FB operate in this successful model?

• Pre-ejection of low-entropy gas:

ejected from progenitors of todays groups/clusters

• Replaced by high-entropy gas that was

never heated by the AGN-driven

• utflow
• Higher entropy  reduced cooling rate
• Nearly all of the action takes places at

high z, when the BHs grew and the stars were formed

McCarthy+ ‘11

Quenching logic (pun intended):

Observations indicate that: 1. Disks are star-forming 2. Bulges are quiescent From this it follows that:

• Quenched galaxies have very high B/T (and associated

properties: e.g. compact, high surface density, high vel. dispersion, high Sersic index)

• Quenched galaxies live in environments that are not

conducive to disk growth

– In orbit around another galaxy; or – At the center of a halo w/o cold flows

• Quenching mechanism must be

– Ineffective in disks, e.g. nuclear outflow – Effective during morphological transformation, e.g. nuclear

• utflow triggered by wet merger or violent disk instability

THANKS TO THE ORGANIZERS!